﻿// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

//
// DependencyGraph.cs: ILLink dependencies graph
//
// Author:
//   Radek Doulik (rodo@xamarin.com)
//
// Copyright 2015 Xamarin Inc (http://www.xamarin.com).
//

using System;
using System.Collections.Generic;
using System.IO;
using System.Xml;

namespace LinkerAnalyzer.Core
{
    public class VertexData
    {
        public string value;
        public List<int> parentIndexes;
        public int index;

        public string DepsCount
        {
            get
            {
                if (parentIndexes == null || parentIndexes.Count < 1)
                    return "";
                return string.Format(" [{0} deps]", parentIndexes.Count);
            }
        }
    }

    public class DependencyGraph
    {
        protected List<VertexData> vertices = new List<VertexData>();
        public List<VertexData> Types = new List<VertexData>();
        readonly Dictionary<string, int> indexes = new Dictionary<string, int>();
        protected Dictionary<string, int> counts = new Dictionary<string, int>();
        internal SpaceAnalyzer SpaceAnalyzer { get; set; }

        public void Load(string filename)
        {
            Console.WriteLine("Loading dependency tree from: {0}", filename);

            try
            {
                using (var fileStream = File.OpenRead(filename))
                {
                    Load(fileStream);
                }
            }
            catch (Exception)
            {
                Console.WriteLine("Unable to open and read the dependencies.");
                Environment.Exit(1);
            }
        }

        void Load(FileStream fileStream)
        {
            using (XmlReader reader = XmlReader.Create(fileStream))
            {
                while (reader.Read())
                {
                    switch (reader.NodeType)
                    {
                        case XmlNodeType.Element:
                            // Console.WriteLine(reader.Name);
                            if (reader.Name == "edge" && reader.IsStartElement())
                            {
                                string b = reader.GetAttribute("b");
                                string e = reader.GetAttribute("e");
                                //Console.WriteLine("edge value " + b + "  -->  " + e);

                                if (e != b)
                                {
                                    VertexData begin = Vertex(b, true);
                                    VertexData end = Vertex(e, true);

                                    end.parentIndexes ??= new List<int>();
                                    if (!end.parentIndexes.Contains(begin.index))
                                    {
                                        end.parentIndexes.Add(begin.index);
                                        //Console.WriteLine(" end parent index: {0}", end.parentIndexes);
                                    }
                                }
                            }
                            break;
                        default:
                            //Console.WriteLine("node: " + reader.NodeType);
                            break;
                    }
                }
            }
        }

        public VertexData Vertex(string vertexName, bool create = false)
        {
            if (indexes.TryGetValue(vertexName, out int index))
                return vertices[index];

            if (!create)
                return null;

            index = vertices.Count;
            var vertex = new VertexData() { value = vertexName, index = index };
            vertices.Add(vertex);
            indexes.Add(vertexName, index);
            string prefix = vertexName.Substring(0, vertexName.IndexOf(':'));
            if (counts.TryGetValue(prefix, out var count))
                counts[prefix] = count + 1;
            else
                counts[prefix] = 1;
            //Console.WriteLine("prefix " + prefix + " count " + counts[prefix]);
            if (prefix == "TypeDef")
            {
                Types.Add(vertex);
            }

            return vertex;
        }

        public VertexData Vertex(int index)
        {
            return vertices[index];
        }

        IEnumerable<Tuple<VertexData, int>> AddDependencies(VertexData vertex, HashSet<int> reachedVertices, int depth)
        {
            reachedVertices.Add(vertex.index);
            yield return new Tuple<VertexData, int>(vertex, depth);

            if (vertex.parentIndexes == null)
                yield break;

            foreach (var pi in vertex.parentIndexes)
            {
                var parent = Vertex(pi);
                if (reachedVertices.Contains(parent.index))
                    continue;

                foreach (var d in AddDependencies(parent, reachedVertices, depth + 1))
                    yield return d;
            }
        }

        public List<Tuple<VertexData, int>> GetAllDependencies(VertexData vertex)
        {
            return new List<Tuple<VertexData, int>>(AddDependencies(vertex, new HashSet<int>(), 0));
        }
    }
}
